Mechanical lead pencil



yum 27, 1939- M. scHAEf-ER MECHANICAL LEAD PENCIL ATTORNEYS 7. l. VM 6 w amv@ my@ n? T Y 1M Patented June v27', 1 939 UNITEDl STATES PATENT OFFICE.

Eagle `Pencil .Compan poration of Delaware y, New York, N. Y., a cor- Apxlucaaon June 2z, 1936, serial No. 86,565

- 5 Claims.

My present invention relates to mechanical pencils, more especially to pencils of the type including an expel movement, that is. a movement for ejecting the short substantially useless'stub of lead that blocks insertion of a fresh lead.

As conducive to a clear understanding of the invention, it is noted that many otherwise satisfactory known mechanical pencils have the limitation that the expel movement thereof has an effective stroke inherently so short that were the writing lead clutched through a' sufficient length to. assure uniform effectiveness of hold, the length of expel stroke would be inadequate to perform its function.

Among the objects of the present invention are to provide a mechanical pencil of the above type in which the expel movement has a stroke of increased length to permit effective ejection of a relatively longer and securely clutched lead extremity, and more particularly to attain the result by a relatively slight modification of known structures, Without the introduction of added elements or added manufacturing cost and without in any way detracting from the effectiveness of otherwise known and approved constructions.

In the accompanying drawings in which are shown one or more of various possible embodiments of the several features of the invention,

Fig. 1 is a view in longitudinal cross-section of a desirable embodiment ofthe' invention,

Figs. 2, 3, 4 and 5 are fragmentary sectional views illustrating successive stages in the operation of the expel movement of the pencil,

Figs. 6 and 'I are transverse sectional views on a larger scale taken respectively on the lines 6-5 and 1-1 of Fig. 1,

Fig. 8 is aperspective fragmentary view on a still larger scale showing the modied lead tube structure, and,

Fig. 9 is a perspective view on a like scale showing the clutch tube and eject plunger combina-` tion.

tion of the inventionA to that general type of mel chanical lead pencil described in greaterdetailv in the prior patent to Isidor Chesler, No. 1,956,271

The accompanying drawing shows an applica- (Cl. 1Z0-18) feed thread I I and having molded into the forward reduced point end thereof a metal ferrule I2.

Extending longitudinally of the case and desirably contacting at its forward end the inner end of the ferrule I2 is a longitudinal lead tube I3 which rides in the bore of the case and is longitudinally slotted to present edges I4 and I5. The lead tube may be bifurcated at its upper end, with legs- I6 bent over to overlap the upper end l0 of the case to b keyed into the eraser ferrule I1 telescoped over said end of the case and rotatable thereon to operate the lead moving mechanism.

A lead propeller shown as a clutch sleeve I8 is l5 slidably mounted in the lead tube. The forward end of the propeller here serves as a clutch I9 to grip the rear end or stub of the writing lead 20. The clutch tube I8 may be made from a blank with its longitudinal edges contacting and af- 20 fording integral lugs 2l on which is preferably mounted the low friction roller 22 to ride in feed track II.

The expel mechanism comprises an expel plunger or pin 23 extending into the rear end of 25 the lead clutch sleeve I8 and is preferably materially longer than the clutch tube. It has a flattened extension 24 affording a shoulder 25 to limit the advance thereof into sleeve I8 and an integral lateral lug 26 to ride in the feed track I I. 30

According to thev present invention, the slot I i--I5 of the lead tube leads into a modified con- `formation at the forward end of said tube which presents an edge extending at an angle relative to said slot and leads to a pointed extremity 21 of 35v the lead tube.

While the front edge conformation joining the extremity 2B of slot edge I5 to the advanced point 21 of the other slot edge I4 may be helical from end to end, and such structure comes within the scope of the invention as claimed, it is advantageous to use the modification of s uch construetion now to be described. As shown, the end edge of the tube I3 extends substantially peripherally at 29 for approximately half the circumference from the forward extremity 28 of slot edge I5 and there. merges into helical edge 30 leading for approximately a half turn to the advanced point 21. Y

In the course of feed operation, the roller or lug 22 on the clutch I 8 in time approaches the end. 28 of the shorter slot. edge I5 as shown in Fig. 2. After the lug 22 of the clutch has passed the end 28 of slot edge I5, the further rotation of lead `tube I3 through substantially a half turn occurs 55 without longitudinally advancing or otherwise moving the clutch tube lug 22, since the transverse forward edge 2l of the lead tube rides thereover. This stage of the operation is shown in Fig. 3. In further rotation, the lug 22 of the clutch is pushed by the helical edge 3l! of the lead tube Il as shown in Fig. 4, to resume its longi- -tudinal advance, but at rate considerably retarded as compared with the rate of advance effected where the pushing edge or slot extends longitudinally. Finally, as shown in Fig. 5 the i lug 22 has bottomed against the metal ferrule I2 and can proceed no farther, in which position it has also reached the point extremity 21 of the lead tube il.

As also appears in Fig. 5, the eject plunger or pin 23 protrudes materially beyond the clutching end of the clutch tube I8 when it reaches the extremity of its eject stroke, thereby to assure effective clearing of the clutch tube' of any particles of lead and to give a clearly visible indication to the user that the lead stub has in fact been completely removed.

It is seen that in the travel oi' lug 22 from the position shown in Fig. 2 to that shown in Fig. 5, a slippage of practically a complete turn of the lead tube I3 relative. to the lug 22 has occurred. No such slippage of the ejector plunger 23 has, however, taken place, since its lug 2l has throughout remained confined by slot il-IB of the lead tube I3. During this action, therefore, the ejector plunger or pin 2l has advanced within the clutch y tube through a range substantially equal to the full pitch of the feed track ,or screw Il, which in al desirable construction is equal to 0.2 inch. Accordingly, it is possible and is preferred to clutch within the lower extremity of the clutch l tube i8 a length of lead of 0.140 inch which is yquite effective for secure hold, as compared to the much lesser clutched length used where only a short stroke of eject movement is available.

The eject action it is seen, occurs in two stages,

in one of which the clutch lug 22 does not advance' at all during a partial rotation of the lead tube and in the final step of which it does advance but at a rate retarded as compared with that of the eject pin lug 26. 'I'he eject mechanism is, accordingly, eil'ectively started to dislodge the lead stub by complete stoppage of the clutch tube and application of the complete propulsive force for advance of the elector plunger. After the stub has thus been loosened the expel action is completed, though more gradually, the expel plunger advancing relative to the more slowly advancing clutch.

By the simple arrangement set forth for bringing about the enhanced stroke of eject movement, the lead tube is not weakened becausev the protruding generally triangular tongue 3l has considerable mechanical strength in view of its lonlug 22 used in the construction shown and even to propel lugs of other types that impose considerably more friction.

' Having thus described my invention, what I claim as newand desire to secure by Letters Patent of the United States is:

l. A mechanical pencil comprising a case having a helical feed thread therein and rigid therewith, a rotatable longitudinally slotted lead tube in said case, a lead propeller tube in said lead tube having a lug protruding through said slot into the feed thread, a lead expel pin in said propeller tubefhaving a lug also protruding through at its forward end for gripping the rear end of 'presenting an inclined surface determining a hellongitudinal slot to afford room for nearly a' com- 5 plete rotation of the lug on the lead propeller after the latter has reached the extremity of its confined course along the lead tube slot, thereby to permit a substantial advance of the lug on the expel pin.

2. A mechanical pencil comprising a case having a feed thread therein and rigid therewith, a longitudinally slotted lead tube lodged in said case and rotatable from the rear end thereof, a lead propelling clutch member longitudinally slidable in said lead tube and having a lug extending through the slot of said lead tube into the feed thread, an expel member having a pin to abut the lead in said clutch and having a lug extending through the slot of said lead tube into said feed thread and trailing behindthe lug on said clutch member, meansnnear the forward end of the case to limit the further longitudinal advance of the clutch tube lug, said lead tube having an inclined forward edge terminating substantially 25 at a point and admitting of rotation of the clutch tube lug for nearly a complete turn relative to said lead tube, whereby a substantial advance of the lug of the expel member is permitted for effective expulsion of a substantial length of lead 3( said case, terminating near the forward end 3;

thereof, a lead propeller in said lead tube having means at its forward end for clutching the rear end of a writing lead and having a lug protruding through the slot of said lead tube andy riding in said feed thread, a lead expel pin in said lead pro- 4| peller and having a lug protruding through the slot of said lead tube into said feed thread to trail the lug on said lead propeller, the forward end of said lead tube having a lug guide conformation continuous with one of the edges of 4` the longitudinal slot thereof, and leading to a point at the forward extremity of the lead tube and permitting slip of the lead propeller lug through nearly a complete revolution relative to the lead tube after the clutch lug passes the 5 lower extremity of the longitudinal slot of the lead tube.

4. A mechanical pencil comprising a case having longitudinallythereof and rigid therewith a feed thread, a longitudinally slotted lead tube l extending substantially the length of said pencil and rotatable from the rear end thereof, said tube terminating near the point of said pencil, a lead clutch tube in said lead tube having means the writing lead and having a lug protruding through the slot of said lead tube and riding in said feed thread, a lead expel pin in said lead clutch tube having a lug protruding through the slot of said lead tube into said feed thread to trail the lug of said clutch tube, the forward end of said slotted lead tube having one side of the longitudinal slot thereof terminating at an advanced point on Asaid tube materially beyond the other edge of said slot, the forward edge of said lead tube beyond the latter edge of the slot thereof ically directed edge from the forward point. merging with a generally semi-circular squareended edge leading to the inner edge of the longitudinal slot.

5. In a mechanicalpencil of the propel-eject type, comprising a case having a lead feeding means, a movable lead holding clutch coasting with said lead feeding means, a. movable eject plunger also coactirg with said lead feeding means, and movable in synchronism with said clutch through substantially its entire course but automatically advanced relative thereto to perform its eject action when the clutch approaches the forward end of its course; the combination therewith of means for continuing the forward propulsion of the eject plunger, while interrupting that of said clutch near the forward end of the stroke thereof, for loosening a. lead stub lodged in said clutch and means for thereupon resuming the longitudinal advance of the clutch to the extremity of its course, at a rate retarded relative to 'that of the continued advance of the eject plunger for iinal expulsion of such lead stub.

MAX SCHAEFER. 

